Recently, an ophthalmologic apparatus using optical coherence tomography (OCT) (hereinafter, sometimes referred to as “OCT apparatus”) that utilizes interference produced by low coherence light are being developed for practical use.
An OCT apparatus can obtain a high resolution tomographic image by irradiating measurement light on a sample and causing the backward scattering light from the sample (returning light) to interfere with reference light. Since the OCT apparatuses can acquire a tomographic image of a retina in a fundus of a test eye and an anterior eye, the OCT apparatuses are widely utilized to perform ophthalmologic diagnosis of the retina, cornea, and the like.
For example, for measurement performed by OCT in ophthalmologic diagnosis of the retina, there is a risk of positional deviation or missing in the tomographic image occurring due to movement of the eyeball, as represented by involuntary eye movement during visual-fixation. Especially, when measurement is performed at a wide angle of view, since it takes time to acquire the tomographic image, there is an increased chance of this risk occurring.
Accordingly, to shorten the measurement time, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2008-508068 discusses a method that uses a plurality of measurement light beams (hereinafter, sometimes simply referred to as “beams”) to narrow the measurement region per beam. According to Japanese Unexamined Patent Application Publication No. 2008-508068, an interferometer splits the plurality of beams respectively into measurement light beams and reference light beams. The interference light produced by each of the beams is dispersed, and the dispersed interference light is detected by a two-dimensional sensor array that is the same for all of the plurality of beams.
However, with the technique discussed in Japanese Unexamined Patent Application Publication No. 2008-508068, the position of the plurality of measurement light beams with respect to the structure of the test eye cannot be adjusted.
Further, when imaging of the test eye is performed at an especially wide angle of view with a plurality of beams, depending on the test eye, focal position deviation can occur between the center and the periphery. For example, when an image plane of the measurement light is determined so that scanning is performed based on a test eye that has a normal refractive power, focal position deviation can occur for a myopic test eye.